This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2003-004435, filed Jan. 10, 2003, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optimum lens system suitable for the optical communication field, an optical system for optical communications such as optical communication components utilizing such an optical communication lens system, and a method of manufacturing the same.
2. Description of the Related Art
Optical communication components as proposed in Jpn. Pat. Appln. KOKAI Publication No. 8-286076 often have problems in coupling with optical fibers. For example, in optical isolators and optical circulators, light transmitted in the optical fibers is once taken out of the optical fibers, and is processed as desired, and put back into the optical fibers. In this process, the light loss must be minimized. Alternatively, when using a laser diode (LD), the laser light oscillated from the LD must be inserted into the optical fibers at as high a coupling efficiency as possible.
Lenses are widely used in order to enhance the coupling efficiency between optical communication components and optical fibers. Examples of lenses used in such a case include a ball lens, a spherical lens, an aspherical lens, and a graded index lens. Above all, the radial type graded index lens (hereinafter called GRIN lens) of tubular shape and having refractive index distribution in the radial direction is widely used because of its ease of alignment in assembling.
Communication traffic is expanding explosively, and the wavelength bands of light for use in optical communications are extending yearly. In future, it is predicted that light of a wide band extending up to 1250 to 1650 nm may be transmitted in a single optical fiber. Further, an Er-doped fiber amplifier which is one of the indispensable technologies in optical communications may use excited light of 980 nm in order to amplify the optical communication wave band of around 1550 nm. In such a case, lights of a very wide band of 980 to 1650 nm coexist in the same optical fiber. Accordingly, the lens system for optical communications for use in the Er-doped fiber amplifier or the like is desired to function favorably in the optical communication wavelength band of 980 to 1650 nm.
According to a first aspect of the present invention, there is provided an optical system for optical communications, comprising a graded index lens composed of a transparent material including at least one metal oxide with valence of 2 or more, and having a refractive index distribution formed by changing the molar ratio of the metal oxide.
According to a second aspect of the present invention, there is provided a method of manufacturing an optical system for optical communications, comprising: forming a transparent material having a refractive index distribution by changing the molar ratio of metal oxide with valence of 2 or more; and configuring a graded index lens from the transparent material.
Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.